Method and apparatus for monitoring polyolefin production

ABSTRACT

The present technique provides for the use of spectroscopic probes, such as Raman probes, within the conduits of a polyolefin production system. The Raman probe or other spectroscopic probes may be used to obtain spectroscopic measurements of the contents of the conduits. The spectroscopic measurements may be processed and analyzed to determine the composition of the conduit contents. In addition, the spectroscopic measurements may be used in conjunction with correlations or other statistical models to determine one or more properties of interest of a constituent of the conduit contents. One or more processes upstream and/or downstream of the conduit may be adjusted in response to the determined composition or composition properties.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application U.S. Ser. No. 10/758,454, filedJan. 14, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the monitoring and/or controlof chemical and petrochemical production and, more specifically, to theuse of Raman spectrometry in the monitoring and/or control of polyolefinproduction.

2. Description of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

As chemical and petrochemical technologies have advanced, the productsof these technologies have become increasingly prevalent in society. Inparticular, as techniques for bonding simple molecular building blocksinto longer chains, or polymers, have advanced, the polymer products,typically in the form of various plastics, have been increasinglyincorporated into various everyday items. For example, polyolefinpolymers, such as polyethylene and polypropylene and their copolymers,are used for retail and pharmaceutical packaging, food and beveragepackaging (such as juice and soda bottles), household containers (suchas pails and boxes), household items (such as appliances, furniture,carpeting, and toys), automobile components, pipes, conduits, andvarious industrial products.

Specific types of polyolefins, such as high density polyethylene (HDPE),have particular applications in the manufacture of blow-molded andinjection-molded goods, such as food and beverage containers, film, andplastic pipe. Other types of polyolefins, such as low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), isotacticpolypropylene (iPP), and syndiotactic polypropylene (sPP) are alsosuited for similar applications. The mechanical requirements of theapplication, such as tensile strength and density, and/or the chemicalrequirements, such thermal stability, molecular weight, and chemicalreactivity, typically determine what polyolefin or type of polyolefin issuitable.

One benefit of polyolefin construction, as may be deduced from the listof uses above, is that it is generally non-reactive with goods orproducts with which it is in contact. This allows polyolefin products tobe used in residential, commercial, and industrial contexts, includingfood and beverage storage and transportation, consumer electronics,agriculture, shipping, and vehicular construction. The wide variety ofresidential, commercial and industrial uses for polyolefins hastranslated into a substantial demand for raw polyolefin which can beextruded, injected, blown or otherwise formed into a final consumableproduct or component.

To satisfy this demand, various processes exist by which olefins may bepolymerized to form polyolefins. Typically, these processes areperformed at petrochemical facilities, which have ready access to theshort-chain olefin molecules such as ethylene, propylene, butene,pentene, hexene, octene, and other building blocks of the much longerpolyolefin polymers. Regardless of which process is used, the polyolefinproduct may deviate from the desired product in various ways. Forexample, the polyolefin product may have a different mechanicalproperties, such as density, hardness, or flexibility, and/or chemicalproperties, such as melting temperature or melt flow index, than what isdesired. These deviations may arise for various reasons, such as varyingcatalyst activity, reactant purity, improper reaction conditions,transitions between product grades, and so on. However, if the deviationis not discovered until late in the reaction process, significantresources, both in material and energy, may be spent producing anunacceptable polyolefin product.

Similarly, after the polyolefin product is produced, further downstreamprocessing, such as extrusion and additive addition, may occur. Thesedownstream processes offer further opportunity for deviation from thedesired final product and may also result in wasted resources if thedeviations are not discovered in a timely manner. Therefore, both in theproduction and in the processing of the polyolefin product, it isdesirable to discover deviations as rapidly as possible and, whereappropriate, to make corrections to the processes to minimize the wasteof product or resources.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 is a block diagram depicting an exemplary polyolefinmanufacturing system for producing polyolefins in accordance with oneembodiment of the present techniques;

FIG. 2 is a flow chart depicting a monitoring routine in accordance withone embodiment of the present techniques;

FIG. 3A is a block diagram depicting automatic monitoring of a sampleenvironment in accordance with one embodiment of the present techniques;

FIG. 3B is a block diagram depicting semi- automatic monitoring of asample environment in accordance with one embodiment of the presenttechniques;

FIG. 3C is a block diagram depicting manual monitoring of a sampleenvironment in accordance with one embodiment of the present techniques;

FIG. 4 is a block diagram depicting the components of a Ramanspectrographic system in accordance with one embodiment of the presenttechniques;

FIG. 5 is a block diagram depicting the components of a portable Ramanspectrographic system in accordance with one embodiment of the presenttechniques;

FIG. 6 is a cross-section taken along the axis of an exemplary Ramanprobe tip in accordance with one embodiment of the present techniques;

FIG. 7 is a cross-section taken along the axis of a sapphire lens foruse in a Raman probe in accordance with one embodiment of the presenttechniques;

FIG. 8 is a cross-section taken along the axis of a Raman probe tiphousing a mushroom-shaped lens in accordance with one embodiment of thepresent techniques;

FIG. 9 is a cross-section taken along the axis of a Raman probe tip forhousing a lens in accordance with one embodiment of the presenttechniques;

FIG. 10 depicts an insertion/retraction apparatus for inserting a Ramanprobe into a reaction chamber in accordance with one embodiment of thepresent techniques;

FIG. 11 depicts a Raman spectrum for use in calibration in oneembodiment of the present techniques;

FIG. 12 depicts two filtered Raman spectra for use in calibration in oneembodiment of the present techniques;

FIG. 13 is a cross-section taken along the axis of a sapphire lensincorporating a spinel material for use in a Raman probe in accordancewith one embodiment of the present techniques;

FIG. 14 depicts a Raman spectrum from a spinel lens and a white lightspectrum in accordance with one embodiment of the present techniques;

FIG. 15 depicts a Raman spinel spectrum combined with the spectrum froma polyethylene sample in accordance with one embodiment of the presenttechniques;

FIG. 16 depicts the Raman polyethylene spectrum after subtraction of thespinel spectrum in accordance with one embodiment of the presenttechniques;

FIG. 17 is a cross-section taken along the axis of an exemplary Ramanprobe tip incorporating a diamond component in accordance with oneembodiment of the present techniques;

FIG. 18 is a side view of a cylindrical valve for use in calibration inone embodiment of the present techniques;

FIG. 19 is a front view of the valve of FIG. 18;

FIG. 20A is a block diagram depicting manual adjustment of a productioncontrol in accordance with one embodiment of the present techniques;

FIG. 20B is a block diagram depicting one method of partially automatedadjustment of a production control in accordance with one embodiment ofthe present techniques;

FIG. 20C is a block diagram depicting another method of partiallyautomated adjustment of a production control in accordance with oneembodiment of the present techniques;

FIG. 20D is a block diagram depicting another method of partiallyautomated adjustment of a production control in accordance with oneembodiment of the present techniques;

FIG. 20E is a block diagram depicting automated adjustment of aproduction control in accordance with one embodiment of the presenttechniques;

FIG. 21 depicts a reactor feed system including flow controllers andcontrol valves in accordance with one embodiment of the presenttechniques;

FIG. 22 depicts a hydrogen feed system in accordance with one embodimentof the present techniques;

FIG. 23 depicts a catalyst feed system in accordance with one embodimentof the present techniques;

FIG. 24 depicts an exemplary loop slurry reactor in accordance with oneembodiment of the present techniques;

FIG. 25 depicts an exemplary gas phase reactor in accordance with oneembodiment of the present techniques;

FIG. 26 depicts a reactor train and recovery system in accordance withone embodiment of the present techniques;

FIG. 27 depicts a liquid phase reactor system, reactor feed system, andrecovery system in accordance with one embodiment of the presenttechniques;

FIG. 28 depicts a post-reaction sorting and blending system inaccordance with one embodiment of the present techniques;

FIG. 29 depicts a post-reaction extrusion system in accordance with oneembodiment of the present techniques;

FIG. 30 depicts a rotating sample holder in accordance with oneembodiment of the present techniques; and

FIG. 31 depicts a post-extrusion sorting and blending system inaccordance with one embodiment of the present techniques.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

The present invention provides a novel technique that aids in theproduction of polyolefin and other chemical products. In particular,monitoring and/or control of production are enhanced by the use ofmonitoring equipment, such as Raman spectrographic equipment, whichrapidly provides information about the ongoing processes. The monitoringequipment may be strategically positioned in the production process toallow upstream or downstream adjustment of the process based upon theacquired measurements.

In order to facilitate presentation of the present technique, thedisclosure is broken into a number of sections. Section I provides anoverview of polyolefin production, a discussion of monitoring techniquesand technology, particularly Raman spectrometry, and various controlmethodologies which may be integrated with the monitoring techniques.Section II provides a series of examples of where and how the monitoringand/or control techniques described herein may be employed. Inparticular, the examples provided, while not exhaustive, encompass arange of possibilities in the polyolefin production process as well asin the subsequent sale and manufacture of the polyolefin. In order tomaintain the integrity of these topics and to facilitate description,the reader may, on occasion, be referred to a topic or figures in adifferent section for a more thorough treatment of an aspect of thetechniques.

I. Polyolefin Production Overview

Turning now to the drawings, and referring initially to FIG. 1, a blockdiagram depicts an exemplary manufacturing system 10 for producingpolyolefins, such as polyethylene, polypropylene and/or theircopolymers. One or more reactor feedstocks 12 may be provided to themanufacturing system 10 by a supplier 14 or from local generation and/orstorage capabilities at the system 10. The one or more feedstocks 12 maybe provided via pipeline, trucks, cylinders, drums, or the like. If morethan one feedstock 12 is provided, the feedstocks 12 may be providedseparately or jointly, i.e., mixed. Examples of possible feedstocks 12include various olefin monomers, such as ethylene, propylene, butene,hexene, octene, and so forth.

The reactor feedstock 12 may be provided to a reactor feed subsystem 16that controls the addition rate of one or more reactor feed streams 18to a polymerization reactor subsystem 20. The reactor feed streams 18may be liquid, gaseous, or a supercritical fluid, depending on the typeof reactor being fed. The reactor feed streams 18 may include separateand/or mixed streams of olefin monomers and comonomers as well as chaintransfer agents, such as hydrogen. The feed streams 18 may also includediluents (such as propane, isobutane, n-hexane, and n-heptane),catalysts (such as Ziegler-Natta catalysts, chromium catalysts,metallocene catalysts, and mixed ZN-metallocene catalysts), co-catalysts(such as triethylaluminum, triethylboron, and methyl aluminoxane), andother additives. The feed subsystem 16 controls the addition rates ofthe feed streams 18 to the reactor subsystem 20 to maintain the desiredreactor stability and/or to achieve the desired polyolefin properties orproduction rate. In addition, the feed subsystem 16 may prepare orcondition one or more catalysts for addition to the reactor subsystem20.

The reactor subsystem 20 may comprise one or more reactor vessels, suchas liquid-phase or gas-phase reactors. The reactor subsystem 20 may alsocomprise a combination of liquid and gas-phase reactors. If multiplereactors comprise the reactor subsystem 20, the reactors may be arrangedin series, in parallel, or in some combination configuration.

Within the reactor subsystem 20, one or more olefin monomers, introducedvia the feed streams 18, polymerize to form a product comprising polymerparticulates, typically called fluff or granules. The fluff may possessone or more melt, physical, Theological, and/or mechanical properties ofinterest, such as density, melt index, copolymer comonomer, modulus,crystallinity, melt flow rate, and/or melt index (MFR) and/or copolymercontent. The reaction conditions within the reactor subsystem 20, suchas temperature, pressure, flow rate, mechanical agitation, producttakeoff, and so forth, may be selected to achieve the desired fluffproperties.

In addition to the one or more olefin monomers, the one or more feedstreams 18 may introduce a diluent into the reactor subsystem 20. Thediluent may be an inert hydrocarbon that is liquid at reactionconditions, such as isobutane, propane, n-pentane, i-pentane,neopentane, and n-hexane. Likewise, a catalyst, which is suitable forpolymerizing the monomers, may be added to the reactor subsystem 20 viathe one or more feed streams 18. For example, in a liquid-phase reactor,the catalyst may be a particle added via a liquid feed stream andsuspended in the fluid medium within the reactor. An example of such acatalyst is a chromium oxide containing a hexavalent chromium on asilica support.

A motive device (not shown) may be present within the reactorscomprising the reactor subsystem 20. For example, within a liquid-phasereactor, such as a loop-slurry reactor, an impeller may be present andmay create a turbulent mixing zone within the fluid medium. The impellermay be driven by a motor or other motive force to propel the fluidmedium as well as any catalyst, polyolefin fluff, or other solidparticulates suspended within the fluid medium, through the closed loopof the reactor. Similarly, within a gas-phase reactor, such as afluidized bed reactor, one or more paddles or stirrers may be presentand may mix the solid particles within the reactor.

The discharge 22 of the reactor subsystem 20 may include the polymerfluff as well as non-polymer components, such as monomer, comonomer,catalysts, or diluent, from the reactor subsystem 22. The discharge 22may be subsequently processed, such as by a monomer/diluent recoverysubsystem 24, to separate the non-polymer components 26 from the polymerfluff 28. The untreated recovered non-polymer components 26 may bereturned to the reactor subsystem 20 or may be treated, such as by afractionation and treatment subsystem 25, and returned to the feedsubsystem 16 as purified components 27. The fluff 28 may also bereturned to the reactor subsystem 20 for further polymerization, such asin a different type of reactor or under different reaction conditions,or may be further processed to prepare it for shipment to a customer 30.

The fluff 28 is normally not sent to customers 30 as product. Instead,the fluff 28 is typically sent to an extruder feed subsystem 32 wherethe fluff 28 may be temporarily stored, such as in silos, to awaitfurther processing. Different fluff products 28 may be commingled in theextruder feed subsystem 32 to produce an extruder feed 34 which, whenextruded, will produce polymer pellets 36 with the desired mechanical,physical, and melt characteristics. The extruder feed 34 may alsocomprise additives 38, such as UV inhibitors and peroxides, which areadded to the fluff products 28 to impart desired characteristics to theextruded polymer pellets 36.

An extruder/pelletizer 40 receives the extruder feed 34, comprising oneor more fluff products 28 and whatever additives 38 have been added. Theextruder/pelletizer 40 heats and melts the extruder feed 34. The meltedextruder feed 34 may then be extruded through a die under pressure toform polyolefin pellets 36. The polyolefin pellets 36 may then betransported to a product load-out area 42 where the pellets 36 may bestored, blended with other pellets 36, and/or loaded into railcars,trucks, bags, and so forth, for distribution to customers 30.

A. Monitoring

The present techniques are directed to the incorporation of monitoringtechnologies into the processes described above such that the monitoringdata is rapidly available to an operator and/or to automated routines.The monitoring data may be available in real-time or near real-time,i.e., within five minutes. Furthermore, the monitoring data may beobtained from contents within the production process, i.e., on-line, orfrom samples removed from the production process, i.e., off-line. Ramanspectrometry will be discussed herein as one such possible monitoringtechnology. Though Raman spectrometry and techniques are discussedextensively herein, it is to be understood that the present techniquesare applicable to other monitoring technologies capable of real-time ornear real-time monitoring and capable of use in on-line processing.

For example, referring to FIG. 2, an exemplary monitoring routine 50 isdepicted. The monitoring routine 50 may begin with a data request 52,which may be generated automatically by a computer routine executed at amonitor device 54, such as a source/controller used for Ramanspectrometry, or at a computer or workstation 56 in communication withthe device 54. The data request 52 may also be generated by an operator58 or by an operator 58 in communication with the monitor device 54. Thedata request 52 may be transmitted to a probe 60 or other monitoringapparatus configured to obtain the desired monitor data 62, such as aRaman spectrum, from a sample. The probe 60, in response, transmits theacquired monitor data 62, such as the spectra, to the monitor device 54.

The monitor device 54 may provide the data 62 to a computer or operatorworkstation 56, such as may be found at a distributed control center.The data 62 may then be processed, such as by statistical modeling, atthe computer or operator workstation 56 to a more useful form, such as achemical concentration, a physical, mechanical, or melt property, oreven a recommended action. Alternatively, the monitor device 54, such asa Raman source/detector, may process the monitor data 62 beforeproviding it to a computer or operator workstation 56. As used herein,the monitor data 62 should be understood to encompass not only the rawmonitor data or spectra acquired by the probe 60, but also processedmonitor data, including processed spectra or the results of subjectingraw data to a statistical analysis, such as partial least squaresregression or other regression techniques.

Regardless of the monitoring technology employed, it is anticipated thatthe general monitoring techniques discussed above may be implemented ina variety of ways. For example, referring to FIG. 3A, monitoring may beautomatic with a monitor probe 60 situated in the sample environment 70sending a continuous stream 72 of monitor data 62, such as Ramanspectra, to a monitor device 54, such as a source/detector in Ramanspectrometry. The monitor device 54 may be configured to receive and/orprocess the monitor data 62. Alternately the monitor probe 60 mayautomatically send a discontinuous stream 74 of monitor data 62 to themonitor device 54, such as upon a schedule or upon a conditional basis.For example, the monitor data 62 may be automatically sent when factorssuch as temperature, pressure, time, or product takeoff exceedconfigured threshold values.

Monitoring may also be performed in a partially or semi-automatedmanner, as depicted in FIG. 3B. In such an implementation, some degreeof operator intervention, such as for initiation, execution, and/orsample retrieval, may be involved in the monitoring process. Forexample, the monitor device 54 may transmit a data request 52 to theprobe 60 in the sample environment 70. An operator 58, however, may berequired to take some action to complete the transmission to the monitorprobe 60, thereby initiating data acquisition and return of the monitordata 62. For example, the operator 58 may be required to acknowledge therequest, such as by interacting with the monitor device 54 or anoperator workstation 56, before the request 52 is transmitted to theprobe 60. Likewise, the operator 58 may be required to provide a sampleto be monitored to the probe 60, such as in batch sample or off-linemonitoring process, prior to initiating probe activity.

Alternately, the monitor device 54 may provide the operator 58 with areminder message or data request 52 to prompt the operator 58 to operatethe probe 60. After operation the probe 60 transmits the requested data62 to the monitor device 54. Furthermore, the operator 58 may insteadprompt the monitor device 54 to initiate a data request 52 to the probe60 with the requested data 62 being transmitted to the device 54. Whilethese various possibilities explain some ways in which the monitoringactivity of the monitor device 54 and probe 60 may be partiallyautomated, other combinations of operator action and automated processexist and are to be understood as falling within the scope of partiallyautomated monitoring techniques as used herein. In addition, themonitoring process may be essentially manual, utilizing an operator 58to initiate the monitoring operation, as depicted in FIG. 3C.

The acquired monitor data 62 is then transmitted to the monitor device54.

1. Raman Spectrometry

a. Overview and Exemplary Systems

As noted above, one suitable technique for on-line and substantiallyreal time monitoring of polyolefin production processes is Ramanspectrometry. Raman spectrometry is a form of vibrational spectrometrywhich utilizes a laser to illuminate a sample and analyzes the reflectedor backscattered radiation. The energy shift between the measuredreflected radiation and the laser line, i.e., the wavelength of thelaser, is equal to the vibrational frequencies of the bonds in themolecules being illuminated. The vibrational frequencies depend on themasses of the atoms in the molecules and on the strength of theinteratomic bonds within the molecule, with different bonds, such as C—Hor C—C, being characterized by specific frequencies. The vibrationalfrequency may also depend on the geometric arrangement of atoms in themolecules.

A Raman spectrum generally comprises a plot of the intensity by theenergy shift, i.e., Raman shift, of the reflected radiation. Inparticular, each observation or data point at a wavelength, measured incm⁻¹, comprises a count at that wavelength. The plot of the aggregatedcounts at each wavelength yields the Raman spectrum for the sampleduring the measured time period. For pure samples, the spectrum may beused to directly identify the sample. For complex mixtures or solutions,the frequency composition may be broken down by statistical analyses,such as partial least squares analysis, to determine the composition ofthe sample. In practice, the peak distribution associated with achemical may serve as a known signature or fingerprint for recognizingthat chemical within a mixture or solution. In addition to thesequantitative and qualitative advantages, Raman spectrometry has theadditional advantages of being spatially resolved, i.e., resolvable at adepth within a sample, and of providing rapid, near-instantaneousresponse because sample preparation is generally not required.

An exemplary Raman spectroscopic system 80 is depicted in FIG. 4. Asdepicted the, spectroscopic system 80 may include a source/detector 82which generates laser radiation of one or more specified wavelengths.The laser radiation is transmitted to a Raman probe 84 via a fiber opticcable 86. The cable 86 may be connected to the probe 84 via an opticalconnector/terminator 88 at the end of the probe 84 or may be integrallyconnected to the probe 84. The cable 86 is typically comprised of two ormore fiber optic strands with a portion of the strands, such as the corestrands, configured to carry the laser radiation from thesource/detector 82 to the probe 84 and the remainder of the strands,i.e., the periphery strands, being configured to carry the reflectedradiation to the source/detector 82. The laser radiation passes to andfrom the sample via a lens 90 at the tip of the probe 84 which issubstantially transparent to the incoming and outgoing lightwavelengths.

The source/detector 82 may process the reflected radiation to form oneor more spectra associated with the sample. The source/detector 82 mayalso, by executing various statistical routines such as partial leastsquares regression, derive various sample properties such as chemicalconcentrations and/or physical, mechanical, rheological, and/or meltproperties of components of the sample. Alternatively, thesource/detector 82 may provide the reflected radiation data or spectrato a workstation 56 or computer, for further processing.

The source/detector 82 may incorporate an optical grating through whichthe reflected radiation is passed to increase spatial resolution withina desired range of wavelengths. For example, an 1,800 line per mmgrating increases spectral resolution over the range of 200 to 1,600cm⁻¹, allowing greater discrimination of the crystalline and amorphousbands observed for polyolefins, such as polyethylene.

The workstation 56 may be configured to control the activities of thesource/detector 82. The workstation 56 may be connected to otherprocessor-based systems, such as one or more remote computers 92 and maycomprise part or all of a distributed control center. The distributedcontrol center may receive data from one or more source/detectors 82,each monitoring different stages of the polyolefin production process.It is to be understood that the connections between the varioussource/detectors 82, workstations 56, and/or remote computers 92 may beaccomplished by various means including wired and wireless connections.

Though the above description assumes a large or static implementation ofa Raman spectroscopic system, portable implementations of Ramanspectrometry may also be possible. Referring to FIG. 5, a portableimplementation of a Raman spectrometry system is depicted. The portablespectroscope 100 may include a battery pack or power supply 102, a radiolink 104 or wireless network module, and a portable source/detector 106.The source/detector 106 may be adjacent to a sample chamber 108 whichmay be opened to introduce sample and closed to eliminate lightcontamination during operation. In addition, a processor 110 may bepresent to execute calibration and monitoring routines stored on amemory device 112. The memory device 112 may comprise an optical ormagnetic media, such as a CD, flash RAM, hard disk, or floppy disk. Theprocessor 110 may also control communication between the radio link 104or network module and a remote database or network. An operatorinterface 114 may also be present on the portable spectroscope 100 toallow an operator 58 to activate the unit 100 or initiate a measurement.

b. Probe Design

While Raman spectrometry provides advantages in the detection andquantification of the reactants, products, and/or product propertiesduring polyolefin production, many of the production environments maydamage the exposed equipment, notably the probe, or otherwise impairmeasurements. For example, process environments may expose a probe toextreme temperatures and/or pressures as well as to caustic agentsand/or various particulate adherents. The probe may thereforeincorporate various features to improve survivability and/or facilitateoperation in the process environment. For example, referring to FIG. 6,a probe tip 120 is depicted which includes a curved or ball lens 122which is suitable for use in environments where particulate buildup islikely. The lens 122 is secured within a lens housing 124 in the probetip 120 which may comprise a lens sleeve 126 sized to accommodate thecircumference of the lens 122. The lens 122 may be secured within theopening, such as by a suitable adhesive or by brazing with silver oranother suitable material. In the depicted embodiment a braze seal 128is provided. In addition, a secondary seal 130 may be provided tofurther exclude the environment, such as dust and moisture from theprobe tip 120. The secondary seal 130 may include a window 132transparent to the wavelengths to be transmitted to and from the probetip 120. The secondary seal 130 may also include a collimator region 134which is opaque to the laser and backscatter wavelengths and which helpsto focus the laser beam.

The curved lens 122 may be constructed from sapphire, diamond or othersuitable materials, i.e., materials which transmit the desired lightwavelengths. For example, in one embodiment, a sapphire lens 122 isemployed which is capable of withstanding up to 15,000 p.s.i.g. andwhich has an approximately 2 mm focus point. Referring to FIG. 7, thelens 122 is seen in greater detail. In particular, it can be seen thatthe lens 122 possesses a minimum diameter 140, for insertion in thecylindrical sleeve 126, and a maximum diameter 142. In one embodiment,the minimum lens diameter 140 may be between 4.4 mm and 4.6 mm and themaximum lens diameter 142 may be between 4.6 mm and 4.9 mm. In addition,the lens 122 has an exposed curvature 144 on the end which may contactthe medium being sampled and an unexposed curvature 146 on the endinterior to the probe tip 120. Because of the curvatures 144 and 146,the lens has two different lengths which may be defined, a total length148 and uncurved length 150. The total length 148 comprises the lengthof the lens 122 along its longest axis, i.e., from the apex of theexposed curvature 144 to the apex of the unexposed curvature 146, and inone aspect of the present technique may be between 9 mm and 10 mm. Theuncurved length 150 comprises the length between the curvatures 144 and146 and in one aspect of the present technique may be 7 mm and 7.5 mm.In one embodiment, the exposed curvature 144 is coated with ananti-reflective coating 152 to improve performance by reducing thetransmission of incidental scatter.

The use of spherical or curved lenses 122 may prevent fines or otherparticulates from adhering on the surface of the lens 122 and indeed maybe self-cleaning in a flowing medium. The spherical or curved lens 122may be configured with a constant focus and may therefore be usedwithout the focusing optics associated with flat lenses, such as a focalrod. Alternatively, as depicted in FIG. 8, a mushroom-type lens 154, asopposed to a ball type lens 122, may be incorporated into the probe tip120, providing similar advantages.

A probe tip 120 which accommodates the lens 122 or 154 is depicted ingreater detail in FIG. 9. The lens housing 124 has a length 160, whichin one aspect of the present technique may be between 2 cm and 3 cm, aswell as an outer diameter 162, which may be between 9 mm and 10 mm. Thehousing 124 may have two interior diameters, a lens inner diameter 164,associated with the lens sleeve 126, and a fiber inner diameter 166,sized to accommodate a fiber optic cable 86. In one aspect of thepresent technique, the lens inner diameter 164 may be between 4.75 mmand 5.25 mm and the fiber inner diameter 166 may be between 4.0 mm and4.5 mm. The region connecting the inner diameters 164 and 166 maycomprise a bevel 168, such as a 35° to 60° bevel. A sleeve length 170may be defined as the region of the sleeve 126 between the bevel 168 andthe end of the housing 124 and, in one aspect of the present technique,may be between 4.75 mm and 5.5 mm. In addition, the housing 124 mayinclude a connection bevel 172, such as a such as a 35° to 60° bevel, toaccommodate a fiber optic connector 88 or mating surface connected tothe housing 124. The probe tip 120 may also incorporate a thermocouple174 to measure temperature at the tip 120.

C. Probe Incorporation

The properly configured probe 84 must, of course, be situated in thesample environment 70, such as a production environment, to collectspectra. Insertion of the probe 84 into controlled environments, such asinto a reactor, an extruder, a recovery system, or the various piping,tubes and/or conduits associated with polyolefin production, may requirea variety of insertion/retraction systems 180. In particular, theinsertion/retraction system 180 for a production environment shouldallow easy insertion and retraction of the probe 84 into the environment70 without perturbing the environment 70 or allowing material to flowbetween the production and non-production environments.

For example, an insertion/retraction system 180 configured to situate aRaman probe 84 into a reactor or other controlled environment 70 isdepicted in FIG. 10. As depicted the probe 84 may be encased in aprotective sheath 182 which extends from a reactor wall 184 (184depicted in FIG. 10 is not the reactor wall, rather it is the probe sealhousing). Various seals 186 and bushings 188 may hold the probe 84securely within the wall 184 while maintaining the controlledenvironment 70. Additional seals 186 may be present to maintain thecontrolled environment 70 if the probe 84 is retracted during on-lineoperation. In addition, primary and secondary probe seals 190 and 192,may be present around the probe tip 120 to protect the lens 122 and toprevent leakage of water or reactants into the tip 120. Indeed, opticalelements may be designed to fit within the secondary seal 192 whichwould allow the lens 122 to be removed from the probe tip 120 withoutfear of leakage of the sample medium into the probe 84. The secondaryseal 192 may be coated with an anti-reflective coating 152, as discussedin regard to the lens 122 above, to improve performance. The probe 84 isattached to a rotary handle 194 by a connector rod 196 which allows theprobe 84 to be moved by operating the handle 194. In particular, in thedepicted embodiment, the probe 84 may be inserted or retracted throughthe seals 186 and bushings 188 in the chamber wall 184 by turning theattached handle 194. The rotary handle 194 allows insertion andretraction of the probe 84 to be performed at a controlled speed andalignment.

The depicted embodiment is suitable for insertion and retraction of aprobe 84 into a hostile controlled environment 70, such as the interiorof a polymerization reactor or monomer recovery system. However, othercontrolled environments 70 which operate at less extreme temperature andpressure may incorporate fewer of the depicted features. For example, inan extruder environment, though operating at high temperature andpressure, the probe 84 may be situated above the melt as opposed toimmersed within the sample medium. As a result, the protective sheath182 and lens seals 190 and 192 may be absent. Similarly, within conduitsor piping transporting feedstock or feed streams, the environment 70 maybe at an ambient temperature and/or at less pressure than in a reactionenvironment. In such an environment 70, the one or more seals 186 and orbushings 188 may be reduced in strength or may be absent. Otherproduction environments 70 may be substantially uncontrolled in terms oftemperature and pressure, such as in polyolefin storage bins or silos orabove the extruder feed stream. In such an environment, seals 186 may bereduced or absent as might the controlled insertion and retractionmechanism 194 and 196.

As evidenced by these examples and as will be understood by thoseskilled in the art, the type and number of seals 186 and bushings 188,the presence or absence of a protective sheath 182, and the presence orabsence of a controlled insertion/retraction mechanism 194 and 196 maybe determined based on the environment 70 to be sampled. In general, thegreater the temperature and pressure differentials and the greater theexposure of the probe 84 to the sample and/or particulates in thesample, the greater the need for the protective or ruggedizing measuressuch as those depicted.

d. Calibration

In addition to configuring a suitable Raman probe andinsertion/retraction system 180, the probe 84 and the source/detector 82are typically calibrated to provide consistent Raman shift and intensityresponses in the acquired spectral data 202, referring to FIG. 11. Forexample, one method of calibrating a 532 nm Raman spectrometer usesnaturally occurring spectral bands 204, which may be observed when aspherical sapphire lens is used in the probe. The naturally occurringspectral band 204 appears in the 3,500-4,100 cm⁻¹ region. The locationand intensity of the band 204 provides an internal calibration standard,allowing calibration of the x-axis and y-axis, respectively, of thespectrum. Calibration checks of the source/detector and probe may beperformed continuously and automatically, such as by an automatedroutine.

Similarly, calibration may be performed by measuring the intensity andlocation of the silicon-oxygen (Si—O) Raman band produced by the opticalfiber 86. Referring to FIG. 12, the Si—O band may be isolated in theoverlap region 210 of a laser band pass filter spectrum 212 ofapproximately 785 nm and a shifted spectrum edge filter spectrum 214. Inparticular, in the overlap region 210, some laser radiation excites theSi—O Raman band. The selection of the edge filter limit for passingshifted radiation back to the source/detector 82 allows a small,quantifiable, and consistent Si—O band to be observed at a fixedfrequency which may be used for calibration. Calibration checks of thesource/detector 82 and probe 84 may also be performed continuously andautomatically by an automated routine using the Si—O band.

Alternatively, a lens 122 may be utilized which incorporates a materialwhich superimposes a distinct spectral signature with the other lensmaterials, typically diamond or sapphire. For example, in oneembodiment, a spinel material 220 may be combined with sapphire ordiamond to form a lens 222 incorporating a calibration matrix, asdepicted in FIG. 13. The spinel material 220 may be of varying thicknessand shape. The spinel material's broad band fluorescence signature alongwith the probe and/or sapphire lens peaks can be used as a referencespectrum for both x-axis and y-axis calibration for every spectrumtaken, thus eliminating the need for calibration verification. Thesignature may be used to calibrate the combination of any probe 84 andsource/detector 82.

For example, referring to FIG. 14, a spinel broad band fluorescencesignature 224 obtained using a lens 222 incorporating a spinel material220 is depicted along with a diffuse white light signature 226 of thetype typically used for taxis calibration. The spinel spectrum wasobtained using a 785 nm laser. The spinel signature 224, as can be seen,shows the same characteristics as the white light signature 226. Thespinel signature 224 also shows the same characteristics as the chromiumfluorescent glass proposed by the National Institute of Standard andTechnology for y-axis, i.e., intensity, calibration. The combination ofx-axis and y-axis calibration for every spectrum acquired by a probe tip120 in contact with the sample provides constant and uniformcalibration. In particular, calibration of the entire optical path ofthe light, as accomplished by this technique, is very desirable forcalibration in a production environment.

In this example, the spinel signature 224 is added to the samplespectrum 228 during sample imaging to yield a combined spectrum 230. Thecombined spectrum 230 depicted in FIG. 15 is representative of apolyethylene spectrum added to the spinel signature spectrum 224 asmeasured through a 7.5 mm diameter spinel and sapphire ball lens.Subtraction of the spinel signature 224, as depicted in FIG. 16,provides calibration intensity and wavelength of the data and allows aclean sample spectrum 228 to be obtained for analysis.

Alternately, diamond and sapphire may be incorporated as probecomponents to provide wavelength and intensity calibration during eachscan. Diamond and sapphire may both be used for wavelength calibration,generating peaks at known wavelengths. In addition, diamond may be usedfor intensity calibration, providing predictable counts. In particular,a diamond component 234 may be used in conjunction with a sapphire lens122, such as a ball lens, to provide an intensity calibration duringeach scan.

For example, referring to FIG. 17, a diamond 234 or diamond windowsituated in the collimated portion of the laser beam may provide asuitable signal for intensity calibration, as opposed to otherconfigurations which may provide too large a signal for calibrationpurposes. The diamond and/or sapphire signals may also be used forwavelength calibration, providing good x-axis and y-axis calibrationduring each scan. Additionally both the sapphire 122 lens and thediamond component 234 or window may be constructed to provide primaryand secondary seals 190 and 192 within the probe tip 120 to protect theprobe optics from the sample environment 70, such as dust and moisture.

If other calibration techniques are used, however, verification of thecalibration must typically be performed. Verification usually involvestaking periodic measurements of known reference materials. One way thismay be done is to incorporate a 3-position cylindrical shutter 238, asdepicted in FIGS. 18 and 19, in the probe assembly. For example, theshutter 238 may be used to couple the probe 84 to the production processas a closed ball valve, providing an “O” ring seal to protect the probe84 from exposure to the elements.

The shutter 238, when incorporated into the beam path 240, has threepositions, one open and two closed. In the open position, as depicted,the beam passes through an opening 242 transverse to the cylinder. Thetwo closed positions, however, are separated by 180 degrees on thecircumference of the cylinder and at right angles to the open path, suchthat, in the closed position, the beam strikes one of two recessedsurfaces 244 and 246. Each recessed surface 244 and 246 is embedded withdifferent solid reference materials, such as low density polyethylene,high density polyethylene, or Teflon. Thus, depending on which closedposition is selected, a different reference material is struck by thebeam, allowing additional calibration information to be acquired.

e. Measuring Chemical Concentrations

Once calibrated and situated in the sample location, the Raman probe 84and source/detector 82 may acquire spectral data 202 about the monitoredproduction process. The spectral data 202 may be used, either by thesource/detector 82 or by a connected processor-based system 56, todetermine the chemical constituents of the sample. In particular, whatintensities, i.e., peaks, are present at what wavelengths may be used todetermine what chemicals are present in the sample. In the presence of acomplex sample, i.e., multiple constituents, statistical analyses, suchas least squares partial regression, may be performed on the spectraldata 202 to determine the constituents. In addition, the respectiveconcentration of each constituent in the sample may be determined fromthe sample spectrum using statistical modeling techniques.

Generally, suitable software must be capable of building models betweenspectral data 202 and concentrations and/or other characteristicsdetermined by some other method and which have a relationship to thespectral response. Such software is typical and commercially available.For example, a chemical concentration in a sample may be determinedusing a concentration model. The data underlying the concentration modelmay be acquired from a separate analysis, such as an analysis using astandard with a known concentration. The Raman spectral data 202 orparts of the spectral data 202 resulting from the analysis of the knownstandard may then be correlated to the known sample concentration andused to develop a concentration model. A concentration model may becreated using commercially available software, such as the GRAMS/32 andPLSplus/IQ programs available from Galactic Industries Corporation(Salem, N.H.). The concentration model may be calculated and sampleconcentrations may be determined, such as with the Galactic GRAMS/32program.

One may employ additional statistical or computational analysis toconfirm or refine the correlation between chemical concentrations andthe peaks, i.e., intensities, generated by Raman spectrometry analysis.For example, one may perform partial least squares regression analysis,using the Galactic PLSplus/IQ program. Partial least squares analysisenables the development of a concentration model where one or morecomponents may have some peaks that overlap.

f. Measuring Physical Properties

In addition, properties of the polyolefin itself or percent solids inthe sample may be determined using Raman spectrometry at appropriatelocations within the production process. For example, using the types ofstatistical analysis and applications discussed in regard toconcentration, statistical models can be constructed using percentsolids, physical, mechanical, rheological, and/or melt data from knownsamples to correlate the polyolefin property of interest withcharacteristic Raman spectral data 202. The models can then be used todetermine the percent solids, physical, mechanical, rheological, or meltproperties of the polyolefin in a measured sample. As with theconcentration models, additional statistical or computational analysesmay be used to refine the models.

For example, in one implementation, chemometric models may be used todetermine polyolefin density based on Raman spectral data 202 obtainedusing a low resolution spectrometer and three absorption peaks in the690-1129 cm⁻¹, one broad peak and two medium intensity peaks. Analysistimes are one to eight minutes. The density of polyolefin fluff, melt,or pellets may be measured on-line with a low-resolution (i.e., 15 cm⁻¹)Raman Systems R2001. Modifications may include dark currentoptimization, and x-axis auto-calibration. The statistical modelemployed may be used to evaluate spectra goodness-of-fit, to reject ofoutliers, and to correlate the intensities of the sample spectrum withthe model spectrum.

Higher resolution Raman Systems R2001 may also be used to measurepolyolefin density. In one implementation, an 1,800 line per millimetergrating may be utilized with the Raman source/detector 82 to increasespectral resolution between of 200 to 1600 cm⁻¹. The resulting highresolution spectral data 202 provide greater discrimination ofcrystalline and amorphous bands on the x-axis. Partial least squaresregression analysis may then be used to model the physical, mechanical,rheological, and/or melt property of interest and to thereby determinethe property from sample spectral data 202.

While density is one polyolefin property that can be determined in thismanner, other properties include melt flow rate (MFR), melt index (MI),high load melt index (HLMI), and zero shear viscosity. The full spectraldata 202 may be used in determining these properties or, in the case ofthe 532 nm Raman system, the ratio of C—H stretch to C—C backbone may berelated to molecular weight, and thereby to the property of interest. Asnoted above, this technique may be applied to polyolefin in the fluff,melt, or pellets stages of production. In addition, similar chemometrictechniques may be used to determine percent solids at applicable stagesof polyolefin production, such as in the reactor subsystem 20, reactordischarge, or polyolefin and monomer recovery systems 24.

B. Control

In response to the data 62 acquired by the monitoring techniquesdescribed above, conditions within the production process may beadjusted to produce polyolefin with the desired qualities andcharacteristics. For example, referring to FIG. 20A, a manual process isdepicted whereby a monitor device 54, such as a Raman source/detector82, provides monitor data 62 to an operator 58, such as via a displaydevice 260 or printed report 262. The operator 58, based upon themonitor data 62, may then adjust 264 one or more production parameters,such as by manually adjusting a production control 266 or by executing acontrol routine on a workstation 56 or computer to adjust the productioncontrol 266. The production control 266 may comprise a variety ofcontrols which, upon adjustment, change one or more productionconditions. Examples of production controls 266 include, flow controlvalves or regulators, compressors, displacement pumps, temperatureand/or pressure controls or settings, and speed regulators, such asmight control an impeller or paddle inside a chemical reactor.

The monitor data 62 provided to the operator 58 may comprise theunprocessed measured data, such as one or more sets of Raman spectraldata 202, and/or processed measured data, such as a chemicalconcentration or percent solids measurement or a determination of aphysical, mechanical, rheological, or melt property of the polyolefin,as determined by chemometric methods such as those discussed herein.Indeed, the monitor data 62 reported to the operator 58 may include acombination of these types of data, such as Raman spectral data 202along with the various concentrations, percent solids, or polyolefinproperties which may be relevant to the stage of the production processbeing sampled.

Partially automated control schemes are possible as well. For example,referring to FIG. 20B, an operator 58 may receive the monitor data 62,as described above. The operator 58 may provide the data, or aquantitative or qualitative assessment of the data, into aprocessor-based system, such as an operator workstation 56 or acomputer, such as might comprise part of a distributed control center.The workstation 56 may be configured to receive the data 62 and toexecute one or more analysis routines on the monitor data 62. Suchroutines may include one or more Chemometric modeling routines, such aspartial least squares regression analysis, as discussed above. Theroutines may receive other inputs, such as pressure, temperature, orreactant flow data, from other sources. Based upon the monitor data 62and any other relevant input, the routines may determine, based on theircoding, what if any production process adjustments 264 should be made.The routine may then adjust the respective production control 266 orcontrols, such as via an electrical or pneumatic signal, depending onthe type of control 266 to be affected.

Alternatively, the workstation 56 may receive the monitor data 62directly from the monitor device 54 and may initiate the responsivecontrol adjustment 264 at the approval or prompting of an operator 58,as depicted in FIG. 20C. Similarly, as depicted in FIG. 20D, theworkstation 56 may receive and process the monitor data 56. Instead ofmaking production adjustments 264 automatically, however, theworkstation 56 may display or provide a printed report 262 of theresults of the processing, such as recommended actions, to an operator58 who may make the appropriate adjustments 262 to one or moreproduction controls 266, as discussed above.

Fully automated control schemes may also be implemented, as depicted inFIG. 20E, providing rapid, closed-loop response to deviations from thedesired production parameters or product properties. In such a scheme,the monitor data 62 may be received and processed by a workstation 56,as discussed above, which adjusts 264 one or more production controls266 via electrical or pneumatic signal without operator oversight orintervention.

By these and other responsive control techniques, data 62 fromstrategically placed monitoring devices 54, such as Raman spectrometers80, may be used to reduce polyolefin process and product variability. Asa result, the production of polyolefin product that possesses thedesired physical, mechanical, rheological, and/or melt properties may befacilitated. In addition, production costs may be reduced because ofincreased reaction efficiency and stability, reduced production ofproduct which is not within a customer's specification, i.e.,“off-spec”, during grade transitions, as well as the elimination orreduction of lab costs associated with product quality control.

II. EXAMPLES

By way of illustrating implementation of the monitoring and controllingtechniques discussed herein, various phases of a polyolefin productionprocess will be discussed with integrated monitoring and/or controlmechanisms. The examples provided are not intended to be exhaustive interms of the stages of polyolefin production, the placement ofmonitoring devices 54, the properties monitored, or the possible controlmeasures taken in response to the measurements. Instead one skilled inthe art will understand that the following examples are merelyillustrative of the general principles of the techniques discussedherein and that such principles may be applied in ways which, while notdiscussed by an example, are within the scope of the invention.Similarly, though Raman spectrometry is discussed in the followingexamples, one skilled in the art will understand that other monitoringtechniques may be utilized, provided that they are capable of providingthe monitoring data in the desired time frame and from the desiredsample environment.

A. Reactant Supply

One phase of the polyolefin production process which may benefit fromthe techniques discussed herein is the receipt of one or more reactantsfrom a supplier 14. For example, one or more Raman probes 84 may monitorone or more reactor feedstock components 12 upstream of the reactor feedsubsystem 16, such as at a supplier's facility, between the supplier'sfacility and the reactor feed subsystem 16, or at the entry point to thereactor feed subsystem 16. Spectral data 202 obtained by any one of theRaman probes 84 monitoring the supply streams 12 may be used todetermine if contaminants are present and, if so, at whatconcentrations. For example, Raman spectral data 202 may be obtained forthe individual or combined feedstocks 12, such as monomer, diluent,and/or comonomer, and analyzed for the presence of catalyst poisons,such as moisture, carbon monoxide, carbon dioxide, acetylene, and soforth. As one skilled in the art will understand, the greater thesensitivity of the Raman probe 84 and source/detector 82 employed, thesmaller the concentration of contaminant or catalyst poison which can bedetected.

Detection of contaminants or catalyst poisons in the supplier feedstocks12 by Raman spectrometry may allow a suitable and timely response to beimplemented upstream and/or downstream of the contamination using one ormore of the control mechanisms discussed above. For example, thecontaminated feedstock 12 may be diverted or terminated in favor of aseparate, uncontaminated feedstock 12 prior to delivery to the reactorfeed subsystem 16. In addition, upstream conditions may be adjusted tomaintain or reestablish an uncontaminated supply of feedstock 12, suchas by switching to a fresh monomer treatment bed and/or initiating theregeneration of spent monomer treatment bed. Though monitoring ofreactant feedstock has been discussed in the context of polyolefinproduction, one skilled in the art will readily understand theapplicability of such techniques to the commercial production of otherchemicals as well.

B. Reactor Feed Subsystems

1. Contaminants

Similarly, Raman spectrometry my be used to monitor for the presence ofcontaminants, such as catalyst poisons, within the reactor feedsubsystem 16 or in the one or more feed streams 18 exiting the subsystem16. The respective Raman probes 84 may be placed in the conduits orpumping mechanisms of the feed subsystem 16 and may be used to acquirespectral data 202 which may be analyzed to determine not only thepresence of a contaminant but also the concentration of such acontaminant.

One or more adjustments 264 may be undertaken in response to acontaminant discovered through this monitoring process, a contaminatedfeedstock 12 may be diverted or terminated in favor of an uncontaminatedfeedstock 12. In addition, the pumping operation of the reactor feedsubsystem 16 may be diverted or terminated to prevent a contaminatedfeed stream 18 from reaching the reactor subsystem 20. Notification ofthe contamination may be sent upstream, such as to a supplier 14, if itis determined that the source of the contaminant is upstream. In thismanner, the quality and operability problems associated withcontaminants and catalyst poisons in the reactor subsystem 20 may beavoided.

2. Reactants and Coreactants

The concentrations and ratios of reactants in the one or more feedstreams 18 and in the feed subsystem 16 may also be monitored by Ramanspectrometry. In particular, one or more Raman probes 84 may be insertedinto the feed subsystem 16 or into the conduit or conduits carrying theone or more feed streams 18 to the reactor subsystem 20. The Ramanspectral data 202 obtained by the Raman probes 84 may be analyzed todetermine the concentration of one or more reactants or coreactants,such as monomer 280, diluent 282, and/or comonomer 284, as depicted inFIG. 21.

One or more adjustments may be undertaken in response to the measuredconcentrations. For example, the flow rate of one or more reactants intothe feed stream 18 or into the reactor subsystem 20 may be adjusted,such as via a flow controller 286, 288, and/or 290 or flow valve, toobtain the desired concentration or reactant ratio in the feed stream 18or reactor subsystem 20, as determined by the polyolefin propertieswhich are desired. For example, in polyethylene (PE) production, theconcentration of a comonomer 284, such as hexene, in a combinedmonomer/comonomer/diluent feed stream 18 may be adjusted, by adjustingthe flow rate of hexene into the feed stream 18. Such adjustment may bewarranted if the concentration of comonomer 284 varies due tofluctuations in the recovered components or from drift in the upstreamcomonomer flow meter in the reactor feed subsystem 16. The use of Ramanspectrometry in the feed stream 18 or the feed subsystem 16 maytherefore allow adjustments to be made to reduce or eliminatevariability in the comonomer concentration within the reactor subsystem20, which might otherwise result in variability in the density of thepolyolefin produced.

In addition, the use of Raman spectrometry to monitor reactantconcentrations in the feed stream 18 and/or the feed subsystem 16 mayfacilitate adjusting reactant concentrations when so desired. Forexample, when reactor conditions are changed, such as when a differentgrade of polyolefin is to be produced, Raman spectral data 202 obtainedfrom within the feed stream 18 and/or the feed subsytem 16 may allowadjustments to be made more rapidly and precisely to the reactant flowrates to obtain the desired reactant concentrations or ratios.

3. Hydrogen

Hydrogen 298, another typical feed component of polymerizationreactions, may determine the fluff properties of the producedpolyolefin. In particular, hydrogen 298 may be added to a polymerizationreaction as a chain transfer agent, which affects various polyolefinproduct properties, such as melt flow rate (MFR) and melt index (MI).Therefore, it may be desirable to monitor hydrogen concentration usingRaman spectrometry with probes 84 in the reactor feed subsystem 16and/or in one or more hydrogen feed streams 296 between the feedsubsystem 16 and the reactor subsystem 20, as depicted in FIG. 22. Inparticular, hydrogen concentration may be determined from the obtainedRaman spectral data 202.

Based upon the measured hydrogen concentration or the calculatedhydrogen flow rate into the reactor subsystem 20, it may be desirable toadjust hydrogen concentration or flow rate based upon the desiredpolymer properties. For example, in polyproplyene (PP) polymerization,hydrogen concentration in the liquid phase of a loop slurry reactor maybe adjusted to control the melt flow rate of the produced PP. The meltindex is similarly controlled in PE polymerization processes. To achievethe desired hydrogen concentration, the flow rate of hydrogen 298 fromthe hydrogen source may be adjusted by operation of one or more flowcontrollers 300, valves, and/or compressors controlling hydrogen flowinto the reactor subsystem 20.

4. Catalysts

The reactor feed subsytem 16 may also supply one or more catalysts 306and 308 to the reactor subsystem 20 via on or more catalyst feed streams304. For example, specific catalyst systems for PE polymerization mayinclude single-site metallocene catalysts supported on borate-activatedsilica, metallocene catalysts supported on an organo-aluminoxy compound,or dual-site chromium catalysts supported on calcined aluminumphosphate. In PP polymerization, some examples are chromium oxidesupported on silica oxide (SiO₂), titanium chloride (i.e., TiCl₃ orTiCl₄) supported on either magnesium chloride or silica, or magnesiumcarbonate (MgCO₃) supported on either magnesium chloride or silica. BothPE and PP polymerization may utilize silica-supported metallocenecatalysts with methyl aluminoxane (MAO) co-catalysts.

The particles of catalyst 306 and 308 may be diluted in a diluent 282,such as isobutane or mineral oil, in the feed subsystem 16 and fed tothe reactor subsystem 20 via a catalyst feed stream 304. For example,referring to FIG. 23, a block diagram depicts an exemplary catalyst feedsystem 310, which may be a component of the reactor feed subsystem 16.The catalyst feed system 310 may provide a single catalyst 306 or 308 ormultiple catalysts 306 and 308, such as metallocene catalysts, to thereactor subsystem 20. Two or more separate catalysts 306 and 308 may beprovided by the catalyst feed system 310, typically at a ratio and rateoptimized to yield the desired polymerization reaction in the reactorsubsystem 20. As depicted, catalysts A 306 and B 308 may be fed to firstand second catalyst mix tanks 312 and 314 respectively. Catalyst A 306and B 308 may be fed to the mix tanks 312 and 314 in a variety of ways.For example, a catalyst 306 or 308 may comprise a slurry which may befed to the respective tank 312 or 314 via process piping. Alternately, acatalyst 306 or 308 may be provided in the form of dry, solid particleswhich are manually fed to the respective tank 312 or 314 from catalystdrums. A diluent 282, such as isobutane, may be metered to the mix tanks312 and 314 to provide a fluid medium for the catalysts 306 and 308.Agitators 316 or recirculating loops (not shown), may mix the catalysts306 or 308 and diluent 282 to form a catalyst slurry. Catalystpreparation may be a batch process or continuous.

One or more of the catalysts 306 and 308 may be monitored via Ramanspectrometry via the techniques discussed herein. In particular, one ormore Raman probes may be situated in the catalyst feed system 310, therespective catalyst feed stream 304 or streams, and/or the reactorsubsystem 20. For example, a Raman probe 84 may be situated in processpiping downstream of the respective catalyst mix tanks 312 and 314,either before or after the catalyst slurries have been combined, asdepicted in FIG. 23. The respective probes 84 may acquire Raman spectraldata 202, which can be used to determine catalyst concentrations,catalyst flow rates, and the ratio of catalysts to one another. Thesevarious factors may be of interest to maintain the rate ofpolymerization within the reactor subsystem 20, the desired polymerproperties, and/or the stability of the reactor subsystem 20.

In response to the catalyst measurements determined from the Ramanspectral data 202, one or more adjustments 264 may be made to obtain thedesired concentration of a catalyst 306 or 308 or the desired ratio ofcatalysts 306 and 308. For example, one or more valves or flowcontrollers 288, 318, or 320 may be adjusted to alter the flow rate ofdiluent 282 or catalyst 306 or 308 into a mix tank 312 or 314, theagitation rate within a mix tank 312 or 314 may be adjusted, the flowrate of catalyst slurry out of a mix tank may be adjusted, or the flowrate of one or more catalyst feed streams 322 or 324 into a catalystfeed stream 304 or into the reactor subsystem 20 may be adjusted, suchas by a flow controller 326 or 328 or valve arrangement.

Additionally, as will be appreciated by those skilled in the art,catalyst feed systems 310 may include additional processing steps, suchas the use of contact pots, prepolymerizers, and other catalystpreparation vessels. The operating conditions, such as temperatureand/or agitation, of these additional processing steps may also beadjusted in response to the Raman spectral data 202 or the determinationof a catalyst concentration or ratio. Adjustments to these additionalsteps may also be affected by the control techniques discussed hereinand may include changing the set point on a thermostat or adjusting anagitation rate.

C. Reactor Subsystems

The various possible feed streams 18, 27, 296, and 304 processed by thereactor feed subsystem 16, discussed above, supply a reactor subsystem20 with reactants, catalysts 306 and 308, and so forth. The reactorsubsystem 20 itself may comprise one or more polymerization reactors,which may in turn be of the same or different types. Furthermore, inmultiple reactor subsystems, the reactors may be arranged serially or inparallel. Whatever the reactor types comprising the reactor subsystem20, a polyolefin particulate product, generically referred to as “fluff”herein, is produced. To facilitate explanation, the following examplesare limited in scope to specific reactor types believed to be familiarto those skilled in the art and to single reactors or simplecombinations. To one skilled in the art, however, the present techniquesare simply and easily applicable to more complex reactor arrangements,such as those involving additional reactors, different reactor types,and/or alternative ordering of the reactors or reactor types. Sucharrangements are considered to be well within the scope of the presentinvention.

1. Liquid Phase

For example, one reactor type comprises reactors within whichpolymerization occurs within a liquid phase. Examples of such liquidphase reactors include stirred tank reactors, loop slurry reactors 340,autoclaves, tubular reactors, and also boiling liquid-pool reactors. Forsimplicity, loop slurry reactors 340 will be discussed in the context ofthe present techniques though it is to be understood that the presenttechniques are similarly applicable to other types of liquid phasereactors.

Loop slurry reactors 340, as depicted in FIG. 24, are generally composedof segments of pipe connected by smooth bends or elbows such that acontinuous flow path is provided that is substantially free frominternal obstructions. A loop slurry reactor 340, for example, may beused to carry out PE or PP polymerization under slurry conditions inwhich insoluble particles of PE or PP are formed in a fluid medium andare suspended as slurry until removed. The fluid medium may includediluent 282, monomer 280, comonomer 284, additives, as well as any otherdesired coreactants, which are added to the reactor interior via inletsor conduits. Catalyst and hydrogen feed streams 304 and 296 may also bepresent. A cocatalyst may also be present, including catalystactivators, such as triethylaluminum alkyl, neat or diluted (e.g., inhexane). Similarly, one or more “donor” agents may be present, such as asilane, which may be used to control the stereospecificity, and therebythe crystallinity, of the polymerized polyolefin molecules.

The reaction conditions, such as temperature, pressure, and reactantconcentrations, are regulated to facilitate the desired degree ofpolymerization and the desired reaction speed. Temperature, however, istypically maintained below that level at which the polymer product wouldgo into solution. Due to the exothermic nature of the polymerizationreaction, cooling jackets 342, through which a cooling fluid iscirculated as needed to remove excess heat, may be provided aroundportions of the loop slurry reactor 340, thereby maintaining thetemperature within the desired range, generally between 150° F. to 250°F. (65° C. to 121° C.). Likewise pressure may be regulated within adesired pressure range,-generally 100 to 800 psig, with a range of450-700 psig being typical.

Raman probes 84 may be inserted at various points within the loop slurryreactor 340. For example, Raman probes 84 may be inserted, using aninsertion/retraction mechanism 180 such as that depicted in FIG. 10,within the reaction loop, such as near the inlet of a feed stream, nearan impeller 344 to sample the turbulent slurry mixture, and/or within acontinuous takeoff point or settling leg 346 to sample the clear liquidabove the polyolefin fluff 28. Due to the exposure of the probe 84 toadherent particulates, i.e., the polymerizing polyolefin, the probe 84may be fitted with a ball 122 or mushroom type lens 154, such as asapphire ball lens, to prevent particle adhesion, as discussed above. A785 nm Raman system may be used to obtain the measurements. In oneembodiment, the scattered Raman signal may be collected for some period,such as 240 seconds, prior to integration into a spectrum for analysis

The Raman spectral data 202 obtained from within the reactor 340 may beused to determine chemical concentrations and/or the ratios of reactantsor catalysts 306 and 308, as discussed with regard to the reactor feedsubsystem 16. In addition, the Raman spectral data 202 obtained fromwithin the reactor 340 may be used to make other determinations as well.For example, the obtained Raman spectral data 202 may be used todetermine the physical, mechanical, rheological, and/or melt properties,such as density, MFR, MI, crystallinity (such as via the measurement ofxylene insolubles) and/or copolymer content, of the polyolefin fluff 28.Similarly, the Raman spectral data 202 may be used to determine thepercent solids, typically 30%-70% by weight, within the reactor 340. Inparticular, determination of percent solids may be used to measure thedifferential settling gain in different parts of the loop, such as in acontinuous takeoff outlet relative to other portions of the loop.Because spectral data 202 may be obtained in a substantially real timemanner, it may also be possible to determine and track the reaction ratebased upon the known flows into and out of the reactor 340 along withthe measurement of percent solids or other polyolefin measures.

In response to these various possible measurements, the productionprocess may be adjusted. For example, based upon the measurements ofconcentrations or the determined ratios, percent solids or polyolefinproperties the flow rates of one or more feed streams 18, 26, 296, or304 may be adjusted, such as by a valve, flow controller, compressor, ordisplacement pump. In this manner, the concentration of reactants,diluent 282, catalyst 306 and 308, and/or hydrogen 298 may be adjustedbased upon the monitored data, i.e., the Raman spectral data 202, tomaintain reactor stability and/or the uniformity of the properties ofthe polyolefin fluff 28. Similarly, adjustments may be made to thetemperature or pressure within the reactor 340, such as via changing theset point on a thermostat or temperature gauge or the flow rate ofcoolant through the cooling jackets 342. In particular, the temperatureand/or pressure may be adjusted in response to a calculated reactionrate which deviates from the desired rate. In this manner, a consistentpolymer fluff 28 possessing the desired properties may be produced bythe liquid phase reactor 340.

2. Gas Phase

The present techniques may be also be used with a gas phase polyolefinreactor 360, as depicted in FIG. 25. Gas phase reactors 360 typicallyoperate as horizontally-stirred bed, vertically-stirred bed, or as afluidized bed, and at lower pressures than liquid phase reactors. Gasphase reactors 360 typically comprise reactor chambers 362 containingcatalyst 306 and 308 which may become fluidized within a bed ofparticles 364. Additional catalyst 306 and 308 may be added to the bed,such as via a catalyst inlet 366. The gaseous feed streams 18 and 296enter the reactor 360, typically from a distributor 368 on the bottom ofthe reactor 360, such as near the plug flow, and pass through the bed toform polyolefin product. In addition, the recovered components stream 26may enter the reactor 360 in a gaseous form or in a gaseous and liquidform, depending on the degree of condensation in the recoveredcomponents stream 26. The feed streams may include monomer 280,comonomer 284, diluent 282, and hydrogen 298. An additive feed stream,such as a stream of anti-fouling agent may also be present.Additionally, if the reactor 360 is part of a chain of reactors a streamof polyolefin fluff 28 containing active levels of residual catalyst 306and 308 may also be introduced to the reactor 360.

Unreacted gases exit the reactor from the top as an overhead gas stream370 while the polyolefin fluff 28 exits the reactor 360 from a discharge372 at or near the bottom of the reactor 360. The overhead gas stream370 may enter a cyclone 374 where fine polyolefin particulates or“fines” and any catalyst particles are separated from the overhead gasstream 370 and recycled to the reactor 360 as a fines stream 376. Acyclone overhead gas stream 378 also exits the cyclone 374 and maycontain monomer 280, comonomer 284, hydrogen 298 and/or diluent 282. Thecyclone overhead gas stream 378 may be recycled to the reactor 360 or toa recovery system or may be flared.

Gas phase reaction generally provides greater specificity in polyolefincopolymer production than liquid phase reactions, allowing theproduction of specified co-polymers as opposed to polymers in which therespective monomers are randomly distributed. For example, gas phasereactors 360 typically facilitate production of block or heterophasiccopolymers. Additionally, because of the relatively low mass of monomer280 and comonomer 284 present in gas phase reactors 360 compared withthat in liquid phase reactors, the discharge stream produced by the gasphase reactor 360 may be less demanding of a downstream monomer recoveryoperation.

A Raman probe 84 may be situated in the overhead gas stream 370 and/orthe cyclone overhead gas stream 378 to measure chemical concentrations,such as reactant concentrations and/or ratios. Similarly, a Raman probe84 may be situated in the fluidized bed region or the plug flow regionto measure chemical concentrations and/or to determine productproperties such as density, MFR, comonomer content, and so forth. ARaman probe 84 may also be situated at the discharge 372 of the reactor360 to determine the properties of the polyolefin fluff 28 at thislocation. For example, in one implementation, PE copolymerpolymerization may occur within a reactor 360 in a range from 250p.s.i.g to 350 p.s.i.g. A 785 nm low resolution Raman system may acquirespectral data 202, such as via a probe 84 in the overhead gas stream370, which may be used to determine the presence and concentration ofethylene and hexene in the reactor 360. Similarly, a 532 nm laser systemmay be used to obtain the Raman spectral data 202 useful for detectingand measuring hydrogen 298.

In response to these measurements and/or determinations, adjustments 264may be made to the flow rates of monomer 280, diluent 282, comonomer284, hydrogen 298 and/or recycled polymer 384 to obtain the desiredconcentrations within the reactor 360 and/or to produce polyolefin withthe desired properties. In addition, the pressure, temperature, bedlevel, catalyst feed rate, additive feed rate, and so forth, within thereactor 360 may be adjusted in response to the Raman spectral data 202or to properties determined from the spectral data 202, such asmonomer/comonomer conversion rates in the reactor 360 or comonomer 284content in the polyolefin fluff 28. The determination of polyolefinproperties may be made using the chemometric techniques discussedherein.

3. Reactor Trains and Combined Phases

As noted above, the reactor subsystem 20 may comprise more than onereactor, including combinations of liquid and gas phase reactors.Indeed, various reactors and reactor types may be sequentially “trained”together to obtain the desired polyolefin fluff product 28. For example,referring now to FIG. 26, a block diagram depicts an exemplarypolyolefin reactor train 390. The depicted reactor train 390 of thereactor subsystem 20 includes one or more loop slurry reactors 340 withassociated slurry discharges 22, an intervening monomer recovery system392, and one or more gas phase reactors 360. As one skilled in the artwill readily apprehend, the reactor train 390 may instead comprise onlyloop slurry reactors 340, only gas phase reactors 360, or an alternativeorder or sequence of loop slurry reactors 340 and gas phase reactors360. In an alternative embodiment, the loop slurry reactors 340 mayinstead comprise one or more boiling liquid-pool reactors.

The intervening monomer/diluent recovery subsystem 392 processes theslurry discharge 22 through one or more flash vessels to produce aprocessed discharge 394. The processed discharge 394 will typically haveresidual active catalyst 306 and 308 with the processed polyolefin. Agas phase reactor 360 may receive the processed discharge 394 as a feedstream. In addition, the gas phase reactor 360 may receive a comonomer284 feed stream 18 independent of any comonomer feed received by theloop slurry reactors 340. A gas phase reactor overhead system, asdepicted in FIG. 25, may also be present. The polyolefin fluff 28 thatexits the gas phase reactor 360 may be processed by a downstream monomerrecovery subsystem 24, by a second gas phase reactor 360, or by otherdownstream processes. Though the present embodiment is depicted asincorporating an intervening monomer recovery subsystem 392, theintervening recovery subsystem 392 may be absent.

As discussed with regard to FIG. 25, Raman probes 84 may measure monomer280, comonomer 284, and/or diluent 282 concentrations in the overheadgas streams 370 and 378 of the one or more gas phase reactors 360.Similarly, polyolefin properties, such as density, MFR and/or comonomercontent may be measured in the gas phase reactor 360, such as in thebed, and/or in the discharge piping.

In such a train 390, monitoring may occur as discussed with regard toFIGS. 24 and 25 with the additional possibility of monitoring in theintervening monomer recovery system 392, as will be discussed below withregard to monomer recovery system 24. In addition, adjustments andcontrol may generally proceed as discussed with regard to FIGS. 24 and25 with the additional possibility of adjustments to upstream reactorsand processes. For example, chemical concentration measurements orpolyolefin property determinations made from Raman spectral data 202obtained from the gas phase reactor 360 may prompt upstream adjustments.Such upstream adjustments may include adjusting the feed rate of thereactor feed streams 18, 26, 296, or 304 to the loop slurry reactor 340,such as by adjusting a valve, flow controller, compressor, ordisplacement pump. Similarly, gas phase measurements and/ordeterminations may prompt adjustment of the loop slurry reactorconditions, such as to temperature, pressure, or agitation. Inparticular, the desirability of upstream adjustments increases as theresidence time between the respective processes decreases. In addition,as will be discussed in greater detail below, adjustments may be made tothe intervening monomer recovery system 392, such as by adjusting thetemperature or pressure of the recovery system 392, based uponmeasurements or determinations made from Raman spectral data 202obtained downstream.

D. Fluff and Reactant Separation and Recovery

After polymerization of the polyolefin fluff 28 within the reactorsubsystem 22, the fluff discharge 22, containing the polyolefin fluff 28and any residual non-polyolefin contaminants may be separated or, in thecase of catalyst 306 and 308, deactivated. Typically this process isreferred to, somewhat narrowly, as monomer recovery. In general, amonomer recovery subsystem 24 may comprise a series of discrete columns,such as purge columns 400, and/or degas vessels, such as high and lowpressure flash vessels 402 and 404. The columns 400 or vessels 402 and404 may operate in a plug flow or fluidized manner.

Referring now to FIG. 27, a block diagram depicts the monomer recoveryprocess of an exemplary polyolefin production process. The reactorsubsystem 20 produces a fluff containing discharge 22, as discussedabove, which contains residual reactants and/or diluent 282 to berecovered. The discharge 22 may also contain catalyst which, ifpolymerization is completed, may be deactivated by the addition of acatalyst poison, such as carbon monoxide, carbon dioxide, steam, and soforth. The discharge 22 from the reactor subsystem 20 may first enter ahigh pressure flash vessel 402 where the reactants, diluent 282, and soforth are exposed to sufficient temperature to evaporate many of thenon-polyolefin components, which may be removed as and recovered in anoverhead gas stream 406. The recovered components 26 may subsequently beused in future polymerization reactions.

The discharge 22 may be further processed in a low pressure flash vessel404 to recover additional non-polyolefin components 26 from the lowpressure flash vessel overhead gas stream 416. Alternately, thedischarge 22 may be returned to the reactor subsystem 20 for additionalreaction in a different reactor. In such cases, the return polyolefindischarge 408 may enter the monomer recovery subsystem 24 at the lowpressure flash vessel 404 as opposed to the high pressure flash vessel402. After treatment through the low pressure flash vessel 404, thedischarge 22 may be processed by a purge column 400. In some cases thepurge column 400 may utilize a nitrogen gas stream 410 to strip residualmonomer 280, comonomer 284, and/or diluent 282 from the fluff 28. Thepurge column overhead gas stream 412 may then be recycled through areverse osmosis membrane unit 414 to refresh the nitrogen stream 410 forreturn to the purge column 400. The recovered residual components 26,such as monomer 280 and diluent 282, may be flared or recycled. Apurified polyolefin fluff 28 typically results from the passage of thedischarge 22 through the monomer recovery subsystem 24.

Raman probes 84 may be situated to obtain spectral data 202 at variouspoints in the monomer recovery process. For example, Raman probes 84 maybe situated in the vessels 402 and 404, the columns 400, or theinterconnecting conduits between the respective vessels 402 and 404 andcolumns 400. Spectral data 202 obtained in the conduits may be used tomeasure chemical concentrations to determine the quantity ofnon-polyolefin components remaining in the discharge 22 as monomerrecovery progresses. In addition, the spectral data 202 obtained in theconduits may be used to determine one or more of the various physical,mechanical, rheological, or melt properties of the polyolefin fluff 28.Raman probes 84 may also be situated in the respective overhead gasstreams 406, 412, and 416 associated with the vessels 402 and 404 andcolumns 400. Spectral data 202 obtained in the overhead gas streams 406,412, and 416 may be used to measure the chemical concentrations of therecovered components 26, i.e., diluent 282, monomer 280, comonomer 284,and so forth, which may be used to determine the efficiency of therecovery process and/or to properly meter the recovered components 26back into the reactor subsystem 20. Similarly, a Raman probe 84 may besituated downstream of the membrane filter 414 associated with the purgecolumn 400 to obtain spectral data 202 of the filtered nitrogen gas 418being returned to the purge column 400. Spectral data 202 obtaineddownstream of the membrane 414 may be used to measure the chemicalconcentration of recovered components 26 in the purge gas 412 andthereby to determine the relative purity of the purge gas 412.

Different locations of the Raman probes 84 within the monomer recoverysubsystem 24 may offer different advantages. For example, the upstreampositions may provide monitor data with less residence time, i.e., lesstime between the measured point and the control point. Downstreamlocations, by contrast, may offer operability and maintenance advantagesbecause the polyolefin fluff 28 is being monitored at lower pressure andwith less residual monomer 280.

Adjustments may be made to the production process based upon themeasured chemical concentration or the determined fluff properties, asdetermined from the respective Raman spectral data 202. For example, theflow rate of one or more recovered reactants or of diluent 282 into thereactor subsystem 20 may be adjusted in response to the measuredconcentrations of reactants or diluent 282 in the recovered components26 or in response to the determined properties of the polyolefin.Similarly, catalyst addition rate or reactor conditions may be adjustedbased upon the concentration of various reactants in the recoveredcomponent gas streams 406, 412, and 416 or upon the determinedproperties of the polyolefin. Because of the rapid turnaround of theRaman spectrometry system, fluff properties, such as density, MFR,and/or MI, may be determined within five minutes instead of hours, asmay be incurred with laboratory analysis. As a result, adjustments maybe made at the reactor level such that off spec fluff product orvariability in the fluff product is minimized.

In addition, the operating conditions, such as flow rate, temperature,and/or pressure, of the flash chambers 402 and 404 and/or the purgecolumn 400 may be adjusted to improve recovery efficiency in response tothe measured downstream concentration of reactants. Similarly, theoperating conditions of the filter 414 processing the purge columnoverhead gas stream 412 or the addition rate of fresh nitrogen gas 420to the purge column 400 may be altered based upon the reactant anddiluent concentrations measured downstream of the filter 414.

While the depicted embodiment is one possible configuration of a monomerrecovery subsystem 24, various configurations for treating thepolyolefin discharge 22 from the reactor subsystem 20 exist other thanthat described herein. One skilled in the art will understand how thepresent principles may be applied to different configurations of amonomer recovery subsystem 24.

E. Extruder Feed Subsystems

After processing by the monomer recovery subsystem 24, the purifiedfluff 28 may, in some circumstances, be transported to a customer sitefor further processing. Typically, however, the purified fluff 28 isfurther processed to form polyolefin pellets 36 prior to shipment to acustomer 30. In particular, the purified fluff 28 may be fed to anextruder/pelletizer 40 which subjects the purified fluff 28 to heatand/or pressure, extruding polyolefin pellets 36 which may then beshipped.

1. Fluff Blending

Prior to extrusion and pelletization, the various batches of purifiedfluff 28 may be combined and blended to form an extruder feed stream 34.For example, two batches of purified polyolefin fluff 28 with differingproperties may be blended to produce polyolefin pellets 36 withproperties between those of the two batches of fluff 28. For example,polyolefin pellets 36 with desired density, comonomer content, modulus,crystallinity, and/or melt properties may be produced by blending twobatches of fluff 28 with properties bracketing the desired properties.Alternately, small amounts of purified fluff 28 which do not possess thedesired properties may be blended with a large amount of conformingfluff 28 to produce conforming pellets 36.

An example of such a blending system 560 is depicted in FIG. 28. In theexemplary system, incoming purified fluff 28 is sorted, based on itsproperties, to different storage silos 562 and 564, two of which areshown. Based on the desired properties of the pellets 36, fluff 28 fromthe different silos 562 and 564 may be metered into a blending silo 566in proportions that will produce the desired properties upon extrusionand pelletization. The fluff 28 may be blended in the blending silo 566by means of a recirculating system 568 or mechanical agitator. Theblended fluff may then be fed to the extruder/pelletizer 40 as anextruder feed 34.

Raman probes 84 may be located at various points within the blendingprocess. Alternately, sample points may be located at various pointswithin the process whereby an operator 58 may remove a fluff sample fortesting using a handheld Raman device 100, as discussed herein. Forexample, referring to FIG. 28, a Raman probe 84 may be situated, or asample taken, prior to sorting of the fluff 28 into the respectivestorage silo 562 and 564. Similarly, Raman probes 84 may be situated, orsamples taken from, the respective storages and blending silos 562, 564,and 566 or from the discharged fluff blend. Spectral data 202 of theblended fluff comprising the feed stream 34 may be integrated over aninterval, such as 240 seconds, such that the spectral data 202accurately represent the composition of the blend. The Raman spectraldata 202 obtained at these sample points may be used to deriveproperties, such as density, comonomer content, and/or melt properties,of the polyolefin fluff 28 or the blended extruder feed 34.

The determined properties may then be used to adjust the sorting andblending process. For example, fluff properties determined prior tosorting may be used to sort the fluff 28 into the proper storage silo562 and 564, such as by adjusting a three-way valve 570 to direct flowinto particular storage silos 562 and 564. Fluff properties determinedprior to blending may be used to confirm that the fluff 28 selected forblending has the desired properties and that it is added at the properrate or in the right amount to produce the desired blend. Similarly, theproperties of the fluff blend in the blending silo 566 or the extruderfeed 34 may be used to adjust the blending process, such as by changingthe addition rate of fluff 28 from a storage silo 562 and 564. Theproperties of the blended fluff may also be used to determine theproperties of the extrusion process-or whether the blend is out of spec.

2. Additives

In addition to purified fluff 28, whether blended or not, the extruderfeed 34 may also comprise one or more additives to alter the polyolefinproperties or to add new properties to the resulting polyolefin.Referring to FIG. 29, ultraviolet light (UV) inhibitors, impactmodifiers, blowing agents, peroxides, and the like, may be added to theextruder feed 34 to enhance the properties of the polyolefin. Theextruder feed 34 with the additives may then be extruded and pelletizedto form polyolefin pellets 36 with the desired properties.

Peroxides 580 may be added to control the viscosity of the extrudermelt. For example, in PP extrusion, peroxide 580 may break some of thelong polymer chains, thereby lowering the viscosity of the melt andincreasing the melt flow rate. In contrast, in PE extrusion, peroxide580 may promote cross-linking of the polymer chains, increasing theviscosity of the melt and decreasing the melt index. The peroxide 580may be added to the extruder feed 34 by a pump 582 that sprays theperoxide 580 onto the extruder feed 34 via a nozzle 584.

In addition, a UV inhibitor may be added to the extruder feed as apowdered additive 586. The UV inhibitor may absorb or reflect UV lightin a polyolefin product, thereby preventing breakage of the polyolefinchains. In this way, the UV inhibitor may protect the polyolefincomprising whatever final product is formed from the polyolefin. Inaddition, other additives 586 may be added to the feed stream 34, suchas tints or dyes, to make the polyolefin more acceptable for itsintended purpose.

Raman probes 84 may be situated to monitor the extruder feed 34, such asafter the addition of peroxide 580, UV inhibitors, and/or otheradditives 586. The spectral data 202 acquired by the probe 84 may beused to measure the chemical concentration of the peroxide 580 and/orother additives 586 and/or to determine the feed properties, such asdensity, comonomer content, melt flow rate, and/or melt index.Adjustments may be made to the respective addition rates based upon themeasured chemical concentrations. In this manner, the desired amount ofperoxide 580 and/or additive 586 may be added to achieve the desiredpolyolefin property or properties, including melt properties, color, andUV protection, after extrusion.

In addition, a UV analyzer 588 may be combined with Raman spectrometryfor monitoring the extruder feed 34 after application of the UVinhibitor. For example, a dual channel detector 590 having ananalog-to-digital board may be provided to simultaneously measure Ramanspectral signals 202 on one channel and ultraviolet spectral signals 592on the second channel. The Raman spectral data 202 may be used todetermine fluff properties, such as density, comonomer content, and/ormelt properties. The UV signal 592 may be used to monitor additives,such as UV inhibitors, tints, and/or dyes. The resulting simultaneoussignals may be processed and displayed by a computer, such as aworkstation in a distributed control center.

F. Extrusion

Once the extruder feed 34 is formed, by fluff blending and/or theaddition of additives 586 and/or peroxide 580, the feed 34 may beprovided to an extruder/pelletizer 40 as a polyolefin melt. The melt issubjected to heat and/or pressure and extruded through a pelletizer aspolyolefin pellets 36. Once cooled, the pellets 36 may be sorted andloaded in a transport vessel for shipment to a customer 30.

A Raman probe 84 may be situated in the extruder 40 above the melt, suchas in the barrel of the extruder, to obtain spectral data 202 of themelt. In addition, a Raman probe 84 may be situated after theextruder/pelletizer 40 to obtain spectral data 202 of the polyolefinpellets 36. For example, a Raman probe 84 may be situated in a flow ofpellets 36 in a vibrating feeder 594. The probe 84 may be situated sothat it is not in contact with the pellets 36, such as 2 to 10 mm abovethe sample.

Alternately, the pellets 36 may be sampled and Raman spectral data 202obtained off-line. In an off-line context, the pellets 36 may be sampledor they may be formed into a plaque which is sampled. For example, inone embodiment, the hot, typically between 140°-160°, freshly extrudedpellets 36 may be cooled to room temperature in water, causing thepolyolefin to crystallize. The pellets 36 and a measured amount of water596 are placed in a vessel 598 mounted on a rotatable platform 600, asdepicted in FIG. 30. The pellets 36 may be circulated in the water 596and a Raman probe 84 inserted into the water 596. As the pellets 36circulate within the water 596, the Raman probe 84 is focused ondifferent pellets 36, allowing measurements to be made of the differentpellets 36 and spectral data 202 to be integrated which adequatelyrepresents the sample. Based on the integrated spectrum, the density, orother properties, of the pellets 36 may be determined within one minute.The probe 84 may be withdrawn, the rotating stage 600 rotated, such asby a small electrical motor 602, and the probe 84 inserted into the nextvessel 598 for sample measurement.

The Raman spectral data 202 of the melt and/or of the pellets 36 may beused to determine the polyolefin density, comonomer content, modulus,crystallinity, melt flow rate, melt index, or other physical,mechanical, rheological, and/or melt properties or to measure thechemical concentration of one or more additives 586 and/or peroxide 580.Alternatively, the distribution of polymer constituents and/or additives586, such as blowing agents, impact modifiers, and so forth, may bedetermined from the Raman spectral data 202 of the pellets. Based uponthe determined property or properties, various adjustments 264 may bemade to the fluff production process and/or the pellet productionprocess. For example, based upon the determined properties, a differentextruder feed stream 34 may be diverted to the extruder/pelletizer 40 orthe operating conditions of the extruder/pelletizer 40, such astemperature and/or pressure, may be adjusted. Similarly, the blend offluff 28 comprising the extruder feed 34 may be adjusted, as discussedabove, to produce pellets 36 with the desired physical, mechanical,rheological, and/or melt properties.

In regard to the additive 586 and/or peroxide 580 concentrations, anadjustment 264 may be made to the addition rate or rates or to the flowrate of the extruder feed 34. In this manner, a desired concentration orratio per unit of feed 34 may be obtained. The additive 586 and/orperoxide 580 concentration may also be adjusted in response to thedetermined properties of the melt 34 and/or pellets 36. For example, theperoxide addition rate may be adjusted based upon the determined meltflow rate or melt index to obtain the desired melt flow rate or meltindex. Similarly, the operating conditions, such as temperature andpressure, within the extruder/pelletizer 40 may be adjusted based uponthe measured additive 586 and/or peroxide 580 concentrations.

In addition, adjustments 264 may be made further upstream based upon thepolyolefin properties determined from the melt 34 or pellets 36. Inparticular, upstream adjustments may be especially useful in productionschemes having reduced or minimal residence time between the reactorsubsystem 20 and the extruder/pelletizer 40 such as when little or noinventory of polyolefin fluff 28 is maintained between the reactorsubsystem 20 and the extruder/pelletizer 40. In such schemes, thepolyolefin properties determined for the melt 34 or the pellets 36 maygenerate adjustments 264 to the flow rates of one or more reactant feedstreams 18 or to the operating conditions of the reactor subsystem 20,such as temperature and pressure.

G. Storage and Load-Out

The polyolefin pellets 36 produced by the extrusion/pelletizationprocess may be sorted and stored or loaded for shipment to customers 30.Though occasionally a customer 30 may wish to purchase the purifiedfluff 28 produced by the monomer recovery process, for simplicity thepresent discussion will be limited to load-out of pellets 36. However,one skilled in the art will understand how the present techniques, asthey apply to pellets 36, may be adapted to apply to fluff 28.

1. Pellet Blending

Typically a customer 30 may desire to purchase polyolefin pellets 36having specific physical, mechanical, rheological, and/or meltproperties, such as density, modulus, crystallinity, comonomerconcentration, melt flow rate, and/or melt index. After pelletization,the pellets 36, if not immediately shipped, may be sorted and storedpending load-out and shipment. For example, referring to FIG. 31,pellets 36 having the same properties may be delivered to one or morestorage bins 610 and 612. If the pellets 36 within a bin 610 or 612 meetthe criteria specified by the customer 30, those pellets 36 may beselected during load-out and loaded, such as into hopper cars 614, forshipment to the customer 30. In some circumstances, such as where thepellets 36 are known to be within the customer's specifications, i.e.,“in-spec”, or where immediate shipment is desired, a bin 610 or 612 maybe operated as a “wide” spot in the line, that is, maintained withlittle or no inventory level to provide minimal or reduced residencetime.

However, if no pellets 36 in storage meet the customer's specification,a mixture of pellets 36 which, on aggregate, meet the specification maybe blended from different storage bins 610 and 612. Likewise, smallamounts of “off-spec” pellets 36 may be blended with “in-spec” pellets36 to reduce or eliminate the off-spec inventory while still deliveringan acceptable mixture of pellets 36 to the customer 30. If blending isdesired, pellets 36 from different bins 610 and 612, and presumably withdiffering properties and/or additives, may be blended in pellet blendingbin 616, such as by a recirculating loop or mechanical agitation. Theratio of pellets 36 from each storage bin 610 and 612 may be determinedby the properties of the pellets 36 in each bin 610 and 612 and theproperties desired of the pellet blend 618. In particular, the pelletblend 618 may be composed such that, on aggregate, the blend 618 iswithin the customer's specification, such as for density, MFR, modulus,crystallinity, additive concentrations, and so forth. The pellet blend618 may be loaded out to a vehicle, such as a hopper car 614, fordelivery to the customer 30.

One or more Raman probes 84 may be incorporated into the pellet storageand load-out process. For example, Raman probes 84 may be situated toobtain spectral data 202 of pellets 36 prior to sorting into the bins610 and 612 and/or in the discharge of the storage and/or blending bins610, 612, and 616. The spectral data 202 may be acquired over someinterval, such as 120 seconds, such that the integrated spectrumaccurately reflects a broad sample. The spectral data 202 obtained bythe Raman probes 84 may be used to determine various properties of thepellets 36 or pellet blend 618, such as density, MFR, modulus,crystallinity, and so forth, or to determine the presence ordistribution of one or more additives 586 or polymers in or on thepellets 36.

Based on the measured properties, the pellet sorting and blendingprocess may be adjusted. For example, properties determined fromspectral data 202 acquired between the extruder/pelletizer 40 and thestorage bins 610 and 612 may facilitate the proper sorting of pellets 36into the bins 610 and 612. Properties determined from spectral data 202acquired between the storage bins 610 and 612 and the blending bin 616may prompt a flow adjustment diverting or terminating the flow from astorage bin 610 or 612 if that bin 610 or 612 does not possess pellets36 with the desired properties. If no blending process occurs, spectraldata 202 acquired in the storage bin discharge may prompt the diversionor termination of the flow of off-spec pellets 36 to the load-outprocess. Similarly, spectral data 202 acquired in the blending bindischarge may prompt the diversion or termination of the flow of anoff-spec pellet blend 618 to the load-out process.

2. Load-Out

Absent an indication that the product is off-spec, the sorted or blendedpellets 36 or 618 may be loaded for transport to a customer site. Theload-out process may comprise filling designated containers, such asrailroad hopper cars 614, with the pellets 36 or blend 618 and preparingthe containers or hoppers 614 for transit. Even if the proper pellets 36are loaded, however, the hoppers 614 or containers may becomedisorganized during the process, particularly, if different types orgrades of pellets 36 are being simultaneously prepared for shipment toone or more customers 30. Problems may arise, therefore, when in-specpellets 36 are prepared for a customer 30 but are not properly routedduring load-out due to poor tracking or communication procedures.

Raman spectrometry, particularly in the form of a handheld Ramanspectroscope 100, may be used to improve tracking and to insure customerorders are properly filled. In particular, pellets 36 loaded into ahopper 614 or other vehicle may be sampled using a handheld Raman device100. The Raman spectral data 202 thereby obtained may then be used todetermine one or more Raman properties, such as density, comonomercontent, modulus, crystallinity, melt flow rate, and/or melt index,which have been specified by the customer 30. In addition, the presenceor distribution of one or more additives 586 on or in the pellets 36 maybe determined from the spectral data 202. The determination of theproperty may be made locally, i.e., by the handheld Raman device 100, orremotely, i.e., by a computer or workstation 56 in wireless or radiocommunication with the device 100. Similarly, the Raman device 100 mayupdate a centralized tracking database by wireless or radio means toallow centralized tracking of the load-out process.

Adjustments 264 may be made to the load-out process based upon the Ramanspectral data 202. For example, hoppers 614 may be diverted to anothercustomer 30 or emptied and refilled with different pellets 36 if theyare found to contain off-spec pellets 36. Similarly, upstream blendingor sorting may be adjusted based upon properties determined duringload-out.

H. Customer Receipt and Processing

At the customer site, the pellet shipments are typically received, suchas by hopper car 614, transferred to a storage site, such as a silo, andtested to determine if the polyolefin pellets 36 are in-spec. If thepellets 36 are in-spec, the customer 30 may process them by melting thepellets 36 and forming them into a polyolefin product 620. Thepolyolefin product 620 may be a final product, ready for retail,commercial, and/or industrial sale, or it may be a component to beincorporated into a final product by the customer 30 or a furtherdownstream customer 30. If the pellets 36 are off-spec, however, thecustomer 30 may return the pellets 36 to the polyolefin productionfacility 10 or may mix the pellets 36 with in-spec material to bring theaggregate within the specification.

To facilitate these decisions, the customer 30 may use a Raman device,such as the portable Raman device 100 discussed above, to check theproperties of pellet samples prior to unloading the pellets 36 into thecustomer's storage site. Raman spectral data 202 may be obtained from asample of the received pellets 36, such as density, comonomer content,modulus, crystallinity, melt flow rate, and/or melt index, determined atthe site of receipt. Similarly, the customer 30 may determine thepresence or distribution of one or more additives 586 on or in thepellets 36 from the spectral data 202. Based on the determinedproperties and/or additives, the customer 30 may accept the pellets 36,divert unsatisfactory pellets 36 to other operations, or returnunsatisfactory pellets 36 to the supplier.

Similarly, the customer 30 or downstream customers 30 may use Ramanspectrometry to acquire spectral data 202 of polyolefin products 620,whether final or intermediate, manufactured from the pellets 36, such asby former 622. Such spectral data 202 may be used to determine one ormore properties of interest, whether physical, mechanical, rheological,and/or melt, prior to shipment or acceptance of the product 620. In thismanner, a manufacturer may divert or terminate shipment of anunacceptable product 620 or a purchaser may refuse receipt of such aproduct 620.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the invention is not intended to be limitedto the particular forms disclosed. Rather, the invention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the invention as defined by the following appended claims.

1. A method of operating a feed system for a polyolefin polymerizationreactor, comprising the acts of: exposing contents in a pumpingmechanism within a feed system of a polyolefin polymerization reactor toa radiation emission from a spectroscopic probe; acquiring aspectroscopic signal from the contents on-line in substantiallyreal-time in response to the radiation emission via the spectroscopicprobe; and analyzing the spectroscopic signal to determine a property ofthe contents.
 2. The method as recited in claim 1, comprising the act ofcontrolling the addition rate of the feed stream to the polymerizationreactor in response to the property.
 3. The method as recited in claim1, comprising the act of mixing a plurality of feedstocks in the feedsystem.
 4. The method as recited in claim 1, wherein the polymerizationreactor comprises a loop slurry reactor adapted to polymerize an olefinto form a polyolefin.
 5. The method as recited in claim 1, wherein thepolyolefin comprises polyethylene, polyethylene copolymer,polypropylene, or polypropylene copolymer, or any combination thereof.6. The method as recited in claim 1, wherein the property comprises aconcentration in the contents of a monomer, a comonomer, a diluent, acatalyst, a co-catalyst, a donor agent, hydrogen, an inert component, acontaminant, or a catalyst poison, or any combination thereof.
 7. Themethod as recited in claim 1, wherein the spectroscopic probe comprisesa Raman probe.
 8. A method of monitoring and controlling a polyolefinproduction process, comprising the acts of: receiving a feedstock into afeed system of a polymerization reactor; exposing contents in a pumpingmechanism in the feed system to a radiation emission from aspectroscopic probe; acquiring a spectroscopic signal from the contentsin substantially real-time in response to the radiation emission via thespectroscopic probe; analyzing the spectroscopic signal to determine aproperty of the contents; and adjusting an operation of the polyolefinproduction process based on the property.
 9. The method as recited inclaim 8, wherein the act of adjusting the operation of the polyolefinproduction process comprises the act of adjusting an addition rate of afeed stream to the polymerization reactor.
 10. The method as recited inclaim 9, wherein the act of adjusting the addition rate of the feedstream comprises the act of manipulating the operation of a flowcontroller, a valve, a compressor, or a pump, or any combinationthereof.
 11. The method as recited in claim 8, wherein the act ofadjusting the operation of the polyolefin production process comprisesthe act of adjusting a concentration of a component in a feed stream tothe polymerization reactor.
 12. The method as recited in claim 11,wherein the act of adjusting the concentration of the component in thefeed stream comprises the act of manipulating the operation of a flowcontroller, a valve, a compressor, or any pump, or any combinationthereof.
 13. The method as recited in claim 8, wherein the act ofadjusting the operation of the polyolefin production process comprisesthe act of adjusting a concentration of a component in thepolymerization reactor.
 14. The method as recited in claim 13, whereinthe component comprises a catalyst.
 15. The method as recited in claim14, wherein the concentration of the catalyst is adjusted to control apolyolefin polymer property in the polymerization reactor, a polyolefinsolids concentration in the polymerization reactor, a production rate ofa polyolefin in the polymerization reactor, or a polyolefin slurrydensity in the polymerization reactor, or any combination thereof. 16.The method as recited in claim 13, wherein the component comprises acomonomer.
 17. The method as recited in claim 16, wherein theconcentration of the comonomer is adjusted to control a polyolefinproduct density in the polymerization reactor.
 18. The method as recitedin claim 13, wherein the component comprises hydrogen.
 19. The method asrecited in claim 18, wherein the concentration of hydrogen is adjustedto control a polyolefin melt flow rate in the polymerization reactor, ora polyolefin melt index in the polymerization reactor, or anycombination thereof.
 20. The method as recited in claim 8, wherein theact of adjusting the operation of the polyolefin production processcomprises the act of adjusting an operation of the feed system or thepolymerization reactor, or a combination thereof, to facilitate apolyolefin grade transition in the polymerization reactor.
 21. Themethod as recited in claim 8, wherein the spectroscopic probe comprisesa Raman probe.
 22. A method of using a Raman spectroscopic device in apolyolefin production process, comprising the acts of: exposing a feedfor a polymerization reactor to a radiation emission from a Ramanspectroscopic probe; acquiring a Raman spectroscopic signal from thefeed in response to the radiation emission; analyzing the Ramanspectroscopic signal to determine a property of the feed; andterminating an upstream supply of feedstock in response to the property.23. The method as recited in claim 22, wherein the Raman spectroscopicsignal is acquired via the Raman spectroscopic probe.
 24. The method asrecited in claim 22, wherein the feed comprises an olefin monomer, acomonomer, a diluent, a catalyst, a co-catalyst, a donor, or a chaintransfer agent, or any combination thereof.
 25. The method as recited inclaim 24, wherein: the olefin monomer and the comonomer compriseethylene, propylene, butene, hexene, octene, or decene, or a combinationthereof; the diluent comprises isobutane, propane, n-pentane, i-pentane,neopentane, or n-hexane, or a combination thereof; and the chaintransfer agent comprises hydrogen.
 26. The method as recited in claim22, wherein the feed comprises an on-line mixture in a feed system, thefeed system configured to manage feed components and to deliver a feedstream to the polymerization reactor.
 27. The method as recited in claim22, wherein the Raman spectroscopic signal is acquired in substantiallyreal-time.
 28. The method as recited in claim 22, wherein the feedcomprises an off-line sample collected from a feed system.
 29. Themethod as recited in claim 22, wherein the property comprises aconcentration of an olefin monomer, a comonomer, a diluent, a catalyst,a co-catalyst, a chain transfer agent, a donor, an inert component, acontaminant, and a catalyst poison, or any combination thereof.
 30. Amethod of using a Raman spectroscopic device in a polyolefin productionprocess, comprising the acts of: exposing a feed for a polymerizationreactor to a radiation emission from a Raman spectroscopic probe;acquiring a Raman spectroscopic signal from the feed in response to theradiation emission; analyzing the Raman spectroscopic signal todetermine a property of the feed; and notifying a supplier of afeedstock to adjust a supplier operation in response to the property.31. The method as recited in claim 22, comprising the act of adjusting aflow rate of a feed stream to the polymerization reactor in response tothe property.
 32. The method as recited in claim 22, comprising the actof adjusting a component concentration in a feed stream to thepolymerization reactor in response to the property.
 33. The method asrecited in claim 22, comprising the act of adjusting a ratio of a firstcomponent to a second component in a feed stream to the polymerizationreactor in response to the property.
 34. A method of monitoring apolyolefin production process, comprising: receiving a feedstock into afeed system of a polyolefin reactor, wherein the feed system isconfigured to deliver a feed stream comprising the feedstock to thepolyolefin reactor, and the polyolefin reactor is configured topolymerize at least one olefin in the presence of a catalyst into apolyolefin; placing a Raman spectroscopic probe tip into a processvolume in the feed system; exposing contents in the process volume to aradiation emission from a Raman spectroscopic probe; acquiring a Ramanspectroscopic signal from the contents in substantially real-time inresponse to the radiation emission via the spectroscopic probe;analyzing the Raman spectroscopic signal to determine a property of thecontents; and notifying a supplier of the feedstock to adjust a supplieroperation in response to the property.
 35. The method as recited inclaim 34, wherein the process volume comprises a conduit, a vessel, or apumping mechanism, or a combination thereof.
 36. The method as recitedin claim 34, wherein the feed stream passes through the process volume.37. The method as recited in claim 34, comprising the act of adjusting afeed rate to a polymerization reactor, a feed concentration to thepolymerization reactor, or a concentration in the polymerizationreactor, or any combination thereof, in response to the property.
 38. Aprocess for manufacturing a product comprising a polyolefin, the processcomprising the act of: manufacturing a product at least a portion ofwhich comprises a polyolefin, wherein the polyolefin is produced by amethod comprising the acts of: receiving a feedstock into a feed systemof a polymerization reactor, wherein the feed system is configured todeliver a feed stream comprising the feedstock to the polymerizationreactor, and the polymerization reactor is configured to polymerize atleast one olefin in the presence of a catalyst into the polyolefin;exposing contents on-line in the feed system to a radiation emissionfrom a spectroscopic probe; acquiring a spectroscopic signal from thecontents in substantially real-time in response to the radiationemission via the spectroscopic probe; analyzing the spectroscopic signalto determine a property of the contents; and terminating an upstreamsupply of feedstock in response to the property.
 39. The process asrecited in claim 38, wherein the spectroscopic probe comprises a Ramanprobe.
 40. The process as recited in claim 38, comprising the act ofobtaining the polyolefin.
 41. The process as recited in claim 38,wherein the act of manufacturing comprises the act of processing thepolyolefin to form the product or to form a polyolefin component of theproduct, or any combination thereof.
 42. The process as recited in claim41, wherein the act of processing comprises the act of blending,heating, melting, extruding, injection-molding, blow-molding, forming afilm, incorporating an additive, or any combination thereof.
 43. Theprocess as recited in claim 38, wherein the act of manufacturingcomprises the act of assembling a component formed from the polyolefininto the product.
 44. The process as recited in claim 38, comprising theact of shipping the product or shipping a polyolefin component of theproduct, or a combination thereof.
 45. The process as recited in claim38, wherein the polyolefin comprises high density polyethylene (HDPE),low density polyethylene (LDPE), linear low density polyethylene(LLDPE), isotactic polypropylene (iPP), or syndiotactic polypropylene(sPP), or a combination thereof.
 46. The process as recited in claim 38,wherein the product comprises film, piping, food packaging, beveragepackaging, retail packaging, pharmaceutical packaging, furniture,carpeting, a consumer electronic, a household container, a householdappliance, a toy, an automobile component, or an agricultural product,or a combination thereof.